Environmental Matters - Environmental Sites (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016
Site Contingency [Line Items]
Current Liabilities	$ 13,221	$ 14,475	$ 13,486
Non-Current Liabilities	107,568	105,268	106,883
Gasco/Siltronic Sediments
Site Contingency [Line Items]
Current Liabilities	1,485	869	1,777
Non-Current Liabilities	43,376	43,972	42,991
Other Portland Harbor
Site Contingency [Line Items]
Current Liabilities	1,435	1,970	1,580
Non-Current Liabilities	3,906	4,148	4,541
Gasco/Siltronic Upland site
Site Contingency [Line Items]
Current Liabilities	9,441	10,657	9,033
Non-Current Liabilities	49,319	49,183	51,433
Central Service Center site
Site Contingency [Line Items]
Current Liabilities	31	73	112
Non-Current Liabilities	0	0	0
Front Street site
Site Contingency [Line Items]
Current Liabilities	829	906	984
Non-Current Liabilities	10,788	7,786	7,739
Oregon Steel Mills
Site Contingency [Line Items]
Current Liabilities	0	0	0
Non-Current Liabilities	$ 179	$ 179	$ 179